1. Field of the Invention
The present invention is related to method and apparatus for producing a vacuum. More particularly, the present invention relates to method and apparatus for producing a vacuum employing a nozzle and venturi combination for achieving sub-atmospheric pressures.
2. Brief Description of the Prior Art
Two basic methods of vacuum production are momentum transfer between a working fluid or turbine and a gas being evacuated and trapping of a gas to be evacuated. Momentum transfer is commonly achieved by utilization of jet pumps, turbines, aspirators and diffusion pumps. Gas trapping is achieved by mechanical pumps, cryogenic pumps, and ion pumps.
Commonly, a distinction is made between pumps designed for primary pumping or secondary pumping. Primary pumps are utilized for higher pressure than secondary pumps and their pumping processes become inefficient at lower pressures. Secondary pumps are utilized at very low pressure and usually can not be operated at a pressure higher than one millimeter of mercury or less.
Exemplary of the prior art are the following U.S. Patents:
U.S. Pat. No. 4,632,649 discloses a gas jet pump having a housing and mixing nozzle holder which form a mounting for a mixing nozzle. The pump is used in both the sub-atmospheric range as a backing pump for other vacuum pumps and in the above atmospheric range.
U.S. Pat. No. 4,580,948 discloses a hydrokinetic amplifier with a high momentum transfer co-efficient discloses a hydrokinetic amplifier configured to receive liquid and vapor for condensing the vapor in the liquid, transferring momentum from the vapor to the liquid, and increasing the pressure of the liquid substantially from input to output. The hydrokinetic amplifier includes an acceleration chamber, a diffuser, a vapor nozzle, an annular liquid nozzle and an annular outer vapor nozzle surrounding the liquid nozzle.
U.S. Pat. No. 3,830,064 discloses an injector for furnishing liquid at a low pressure to a vessel at a higher pressure including an enclosed chamber which has at its bottom end a centrally located downwardly converging combining tube, a nozzle centrally supported in the chamber having a downwardly and outwardly directed tube extending through the central opening and terminating in the lower chamber, and a diverging diffuser tube connected to the outlet of the combining tube for slowing the stream and converting its velocity to a pressure head.
U.S. Pat. No. 3,369,735 discloses a gas jet suction device for connection to vacuum pump having an injector unit formed of a mixing tube and a jet nozzle located in the mixing tube, the injector being mounted in the housing structure, the jet nozzle being coaxially seated in the neck portion of the apparatus for driving a gas jet through a tube toward the outlet neck portion.
U.S. Pat. No. 3,064,878 discloses a method and apparatus for producing a vacuum employing a supersonic jet diffuser having a convergent mixing entrance, a turbulence reducing or constant area duct and a diffuser portion having characteristics and being so proportioned as to provide optimum efficiency of fluid flow therethrough upon predetermined pressure conditions of primary and secondary inlet areas.
U.S. Pat. No. 2,183,623 discloses a steam injector, discloses steam jet exhauster which will withstand erosive action of wet steam and the corrosive action of acid and other chemical vapors and fluids. The steam injector includes a nozzle for spraying steam into a vitreous diffuser or venturi.
U.S. Pat. No. 2,085,361 discloses a steam jet exhauster having a nozzle made of carbon for spraying steam located above a diffuser or venturi made from carbon. The carbon resists the erosive action of wet steam and the corrosive of action vapors.
U.S. Pat. No. 1,367,865 discloses a method and apparatus for producing a high vacuum including entraining the gas to be pumped in a jet vapor such as mercury, cadmium, hydrocarbon oils, or the like which has a extremely high velocity and high degree of rarefaction due to having been expanded from a high initial pressure to a considerable lower pressure. The degree of expansion of the jet is such that a specially absorptive condition of the jet is produced enabling the jet to entrain gas whose pressure is only a small fraction of the pressure in the jet.
U.S. Pat. No. 929,674 discloses a water jet apparatus which serves as the propulsive or actuating means in aspirators, exhausters, jet-condensers and similar apparatus. The water jet apparatus includes ribs or grooves in the water jet or jets to break up the outer skin of the jet so that it issues from the orifice in a form of an envelope of separated and partly scattered water particles surrounding an interior solid and compact core.
U.S. Pat. No. 246,149 discloses a hydraulic ventilator utilizing a nozzle discharging water into a cylinder producing a pressure differential at each end of the cylinder. The pressure differential is utilized to propel air through a building or dwelling to purify, moisturize and cool the air.